I have sufficient reason to believe that Square Enix has security issues that compromise their players' logins and passwords. Security Token password is the one thing that hackers can not beat, unless they install certain keylogging software onto your computer, which at that point means your system is compromised anyway.
Don't think of it as just securing your characters, think of it as securing all of your personal data on their websites, since the token, once registered, will be required to log into all website services, too.
After spending some substantial time this evening looking into various claims and reports, I just purchased one for myself.
edit: for those who may not know of what I mean, click this link: http://www.square-enix.com/na/account/otp/